Nachum Ulanowsky 

Aarhus Universitet, Denmark

"Neural anoxia tolerance supported the evolution of sharp vision in birds"

High blood flows are required for vascular perfusion to meet the high metabolic demands of all neural tissues. As an apparent exception, the bird retina is packed with neurons but lacks internal blood vessels to ensure the clear path of the incoming light needed for high visual acuity. Thus, the avascular state of the bird retina questions how oxygen can be supplied to this highly metabolically active tissue and support birds' sharp vision. Using direct in vivo oxygen and CO2 measurements with sharp electrodes in birds, reptiles, and mammals, we show that the bird retina functions under continuous oxygen deprivation (anoxia), which contrasts with the high oxygen levels in the other vertebrate groups. Spatial and single-cell transcriptomics reveals that the high retinal energy metabolism is secured through continuous anaerobic glycolysis supported by a reverse exchange of glucose and lactic acid via the pecten oculi, a conspicuous structure within the bird eye with a previously unknown function. The unique neural anoxia tolerance, likely shaped by a strong natural selection for a thick avascular retina in early bird evolution, provides the biochemical and physiological basis for the sharp vision in birds and a novel and exciting model tissue to understand naturally evolved mechanisms for anoxia resilience in neural tissues.

Host: Henrik Mouritsen

National holiday (Ascension Day)

Henrik Mouritsen

Host: Pauline Fleischmann

guided by Oliver Lindecke

Heiko Schmaljohann

Gabriele Gerlach

Sandra Bouwhuis

Bernd Blasius

Stefan Harfst

CAnMove - Centre for Animal Movement Research, Lund Universitet

Host: Miriam Liedvogel